A bandwidth requirement is generated during an increase in an Internet Protocol service, and a static optical network cannot satisfy an existing requirement. Technologies such as an automatically switched optical network and general multiprotocol label switching develop rapidly based on this. The Internet Engineering Task Force (IETF) proposes a path computation element (PCE) to satisfy a path computation requirement in the technologies such as an automatically switched optical network and general multiprotocol label switching. A main function of the PCE is to perform centralized route computation in a management domain to avoid a resource conflict problem caused by distributed route computation.
A main operating process of the PCE is: After receiving a request of a path computation client (PCC), the PCE returns path information to the PCC according to a routing algorithm and a current available network resource.
After a network scale is enlarged, a single PCE cannot satisfy the path computation requirement. Therefore, a network needs to be divided into multiple management domains (hereinafter referred to as a domain), each management domain has a PCE responsible for path computation, and each PCE interacts interconnected routing information with each other according to a PCE protocol.
At present, when a multi-domain path is being computed, a backward recursive path computation (BRPC) solution may be used to generate a virtual shortest path tree (VSPT), and an optimal path is selected from the virtual shortest path tree to implement path establishment.
In an existing VSPT generation process, every time when a path section is being computed, a resource in a PCE of a corresponding domain needs to be reserved for the path section. When a network scale is relatively large and a quantity of involved domains is relatively large, the VSPT has many branches, and a corresponding resource is reserved on each branch. After a path is established, a reserved resource is not to be released to a resource pool for computation of another path until a specified duration ends. Therefore, in a large-scale multi-domain network, when a path is being computed, several multiples of resources may need to be reserved for a long time, causing low resource utilization efficiency. In particular, when there are many services on a multi-domain path and path computation is required frequently, it is likely to cause a relatively high network congestion rate.